JPH0437131A - Pure water washing vessel for semiconductor wafer and washing thereof - Google Patents

Abstract

PURPOSE:To obtain a treated pure wafer after lessening the quantity of expensive pure water used and shortening the time of treatment thereof as well by allowing this water vessel to be equipped with a trough which is installed around a directly lower part of the outside circumference of a weir that is on the same level surface as that found at the upper edge of the water vessel and a means for maintaining the reference surface of water which makes the surface of water in the trough level or taking the like measures for treating the wafer. CONSTITUTION:In the pure water washing vessel of a semiconductor wafer 6 consisting of: a water vessel 1; a water supply pipe 2a at the lower part of the water vessel 1, and a weir 5 located at the same level surface as that found at the upper edge of the water vessel 1, the water vessel is equipped with a trough 11 which is installed around a directly lower part of the outside circumference of the weir mentioned above and a means 12 for maintaining the reference surface of water which makes the surface of water in the trough 11 level. Further, the surface of the wafer 6 is immersed in the water vessel consisting of the water vessel 1, the water supply pipe 2a, and the weir 5 so that the surface of the wafer is almost perpendicular to the water vessel and pure water is fed from the water supply pipe 2a. When the wafer 6 is washed by overflowing from the weir 5, the device surface 6a of the wafer 6 is tilted downwards supposing pure water flows upwards to the wafer 6 and when the wafer 6 is taken out of the water vessel 1, the device surface 6a is tilted upwards when pure water flows downwards to the wafer 6.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pure water washing tank and a washing method for semiconductor wafers.

[Conventional technology]

Conventional pure water washing baths and washing methods for semiconductor wafers (hereinafter also referred to as wafers) are approximately as follows.

That is, a washing tank consisting of a water tank, a water supply pipe at the bottom of the tank, and a weir at the upper edge of the tank is used, and a large number of wafers are stored in a suitable cassette so that the surfaces of the wafers are almost vertical. The wafer is immersed in the water tank, and pure water is supplied from the water supply pipe to overflow from the weir to wash the wafer.

To take out the washed wafer from the water tank, a drain pipe is provided at the bottom of the water tank, and the pure water is drained from the drain pipe before the wafer is taken out.

Another method for removing the wafer is to pull the wafer out of the pure water without draining the water.

In the latter extraction method, multiple water tanks are prepared, and the wafers are sequentially transferred to the post-process water tank that maintains cleaner pure water, followed by wafers that are less clean, while the pure water is transferred to the post-process water tank that holds cleaner water. The water is sequentially transferred from the water tank to the water tank in the previous process.
A so-called cascade method may also be used.

Further, the weir at the upper edge of the water tank is kept as accurately as possible in the same horizontal plane, and sometimes the upper edge is made serrated over the entire circumference of the tank, thereby forming a large number of triangular weirs around the entire circumference. In this way, the flow rate of pure water overflowing from the weir becomes uniform over the entire circumference, and a uniform flow rate of pure water can be obtained on each surface of a large number of wafers in the water tank. After all, wafers can be processed faster and to the same level of cleanliness using less expensive pure water.

Problem to be solved by the invention C] In the above-mentioned conventional technology, even if the water tank is installed horizontally to ensure that the weir is properly leveled, or a plurality of triangular weirs are formed, there is still a problem that the water overflows from the weir. The flow rate of water may not be uniform around the entire circumference of the weir. This is due to the arrangement of the wafers in the water tank, the fluid resistance of the cassette, and some kind of holder that holds the cassette, which can cause turbulence in the flow of pure water rising in the tank, and deviations in the size and direction of the flow velocity. It turns out that this is the cause.

In addition, it appears that the pure water is not being used effectively, as the pure water rises up the inner wall area of the water tank where there are no wafers, and the pure water that flows between the wafers passes through the tank.

An object of the present invention is to provide a pure water washing tank and a washing method for semiconductor wafers, which can reduce the amount of expensive pure water used, shorten the processing time, and process clean wafers.

[Means to solve the problem]

A pure water washing tank for semiconductor wafers according to the first aspect of the present invention is a pure water washing tank for semiconductor wafers, which comprises a water tank, a water supply pipe at the lower part of the water tank, and a weir located on the same horizontal plane at the upper edge of the water tank, which has the following steps: It is equipped with a gutter that runs just below the outer periphery of the weir, and a reference water surface holding means that maintains the water surface of this gutter horizontally.

Here, the reference water level maintenance means may include, in addition to the water level maintenance pipe shown in the embodiment, a so-called second weir that is lower than the weir depth on the outer periphery of the gutter.

A pure water washing tank for semiconductor wafers according to the second aspect of the present invention is a pure water washing tank for semiconductor wafers, which comprises a water tank, a water supply pipe at the lower part of the water tank, and a weir at the upper edge of the water tank, in which a surface within the water tank is almost completely covered with water. The diaphragm plate includes an aperture plate disposed below a plurality of wafers arranged vertically in parallel, and an opening provided in the aperture plate and located in a region below the plurality of wafers.

Here, the aperture plate may also serve as the holding stand shown in the embodiment, or if the cassette that stores the wafers is hung in a simple bottle in a water tank, the bottom of the cassette may also serve as the aperture plate. It's okay. Furthermore, since the purpose is to effectively apply the water flow to the wafers, a weir may be provided at a part of the upper edge of the water tank, and the weir located on the same horizontal plane as in Invention I is not an essential structure.

The pure water washing tank for semiconductor wafers of invention 3 is arranged above the water supply pipe in the pure water washing tank for semiconductor wafers, which comprises a water tank, a water supply pipe at the lower part of the water tank, and a weir at the upper edge of the water tank. The wafer is provided with a holding table for holding the surface of the wafer substantially vertically, and a tilting means for tilting the holding table.

Here again, the weirs located on the same horizontal plane as in Invention 1 are not an essential structure.

Invention 40 A pure water washing tank for semiconductor wafers is the pure water washing tank for semiconductor wafers according to the second or third aspect of the invention, wherein a drain pipe is provided at a lower part of the water tank.

In addition, this invention 4 can be used for the method of draining pure water from a drain pipe and then taking out a wafer, as explained in the conventional example, and is similar to invention 1.
Items from 3 to 3 can also be used to take out wafers from pure water without draining the water.

In the method for washing semiconductor wafers according to the fifth aspect of the invention, the wafer is immersed with its surface substantially vertically in a washing layer consisting of a water tank, a water supply pipe at the bottom of the water tank, and a weir at the upper edge of the water tank, and pure water is poured into the water supply. In a semiconductor wafer washing method in which the water is supplied from a pipe and overflows from the base to wash the wafer, when the pure water flows upward to the wafer, the device surface of the wafer is tilted downward, and the wafer is washed with water. When the wafer is taken out from the water tank, the device surface is tilted upward when the pure water flows downward with respect to the wafer.

Here, the phrase "when pure water flows downward relative to the wafer" refers to both cases in which the wafer is drained before being taken out, and cases in which the wafer is taken out from pure water without draining, and the wafer and pure water are indicates the relative movement of

[Effect]

In invention 1, the water surface of the gutter directly below the weir exhibits an action similar to that of the water surface downstream of a so-called submerged weir. in general,
There are two types of weir: a normal weir, in which the water level downstream of the weir is sufficiently lower than the weir peak, and the height of the downstream water level has no effect on the flow overflowing the weir, and a submerged weir, in which the downstream water level is higher than the weir peak. is well known. Although it is not a submerged weir, in the case of the configuration of the invention in which the downstream water surface exists directly below the weir, if the downstream water surface is kept constant, there will be no overflow in the upstream area, that is, the high water surface area in the tank. The flow rate of the weir is restricted to a large extent, and the overflow flow rate at the lower part of the weir is less restricted.The downstream water level is kept constant around the entire circumference of the weir by means of the standard water level control means in the gutter. Naturally, the cross-sectional area of the gutter is made sufficiently large, so even if there is some overflow of the flow rate, the effect of keeping it constant will not be impaired.

Now, when we observe the inside of the aquarium, even if the weir is kept correctly level, there is a fairly large difference in the dynamic pressure of the water flow all around the weir due to various fluid resistances within the aquarium.

As a result, more water will flow to certain parts of the weir and less water will flow to other parts. This appears as a deviation in the streamlines and flow velocity within the water tank, causing deviations in the washing effect for each wafer.

However, according to the configuration of the invention, as described above, the water surface of the gutter directly below the weir acts to correct the above-mentioned deviation, thereby making the washing effect uniform for each wafer.

As shown in the example, a triangular weir with a pitch of 3 am,
111 in an aquarium with a horizontal cross section of 18C1l x 35a1 corner
/+++in of pure water, the flow rate per one triangular weir is calculated to be 5.2cc/sec, but when the water level in the gutter is maintained H = 4css lower than the weir, the weir's flow rate is 5.2cc/sec. The flow velocity over the entire circumference was the most uniform, and the water washing effect for each wafer was the most uniform. However, the above-mentioned H is influenced by the size of the tank, the flow rate, and the fluid resistance of the wafers in the tank, the cassette 7), etc.

In invention 2, the flow of pure water is concentrated on the wafer by the diaphragm plate having an opening, so that when the wafer cannot be placed in the entire area of the water tank cross section using the auxiliary member such as the cassette or its handle, the pure water can effectively concentrate on the wafer. Wash with water.

In invention 3, the device surface of the wafer can be tilted downward by tilting the holding table during supply of pure water, and the device surface can be tilted upward when draining water or pulling up the wafer from pure water, as described below. The effect of invention 5 is produced.

In invention 4, a washing tank is configured to take out the wafer after draining water from the drain pipe, and the effect of invention 2 or 3 is produced even when draining water.

In the method of invention 5, when pure water is supplied from the water supply pipe and flows upward to the wafer, the device surface of the wafer is tilted downward, so that the pure water thoroughly washes the device surface.

When draining water from a drain pipe or pulling up a wafer from pure water, the device side is tilted upwards, so the pure water washes the device side thoroughly at this time as well, and washing the device side with water is faster than washing the opposite side of the device. Become good.

〔Example〕

FIG. 1 is a cross-sectional view showing the state of pure water supply in the embodiment, taken along the line I-I in FIG. 3, FIG. 2 is a cross-sectional view showing the draining state in FIG. Partially cutaway front view of Figure 1;
FIG. 4 is a plan view of FIG. 3. In addition, Figures 3 and 4
The figure shows the state without pure water and wafer.

In the figure, two rows of water supply pipes 2 (2a, 2b) with many pores and a drain pipe 4 with a valve 3 are connected to the lower part of a water tank 1 with a rectangular horizontal cross section, and a weir 5 is connected to the upper edge. to form a washing tank. In this example, the weir 5 is made up of a large number of triangular weirs and has a serrated shape, and two cassettes 7 with handles 7a for storing wafers 6 arranged in parallel can be used in the water tank 1, and a water supply pipe 2a.

2b is branched from the external water supply pipe 8. Up to this point, conventional techniques have been used.

Now, according to the first invention, a gutter 11 is stretched just below the outer periphery of the weir 5. This gutter 11 has a water level maintenance pipe 1 as a reference water level holding means to maintain the water surface 11a in the gutter horizontally.
2 is attached. Although it is preferable that the waterway cross section of the gutter 11 be sufficiently large, the outer periphery of the gutter 11 may be set at the height of the water surface 11a, so as to provide a so-called second weir. In any case, the water surface 11a is made to have a height H directly below the weir 5. The water surface 11a is higher than the weir 5, so it is not a so-called speakeasy weir, but the height H of the water surface 11a is higher than a normal weir, which does not affect the flow that overflows the weir 5 at all, and the flow from inside the water tank 1. Dynamic pressure restricts flow that rises higher and overflows, but does not restrict flow that overflows lower as much.

According to experiments, a triangular weir with a height of 0.51 pitch and 3 aa,
18alX35 (I11 in a water tank with a horizontal cross section of
When A/win pure water flows, the flow rate per triangular weir is calculated to be 5.2 cc/sec, but the water level in the gutter was maintained H = 4 (2) lower than the weir. At this time, the flow velocity over the entire circumference of the weir was most uniform, and the water washing effect for each wafer was most uniform. However, the above-mentioned H is influenced by the size of the oak, the flow rate, and the fluid resistance of the wafers, cassettes, etc. in the water tank.

Next, according to inventions 2 and 3, the cassette 7 is placed on a holding table 14 which can be tilted by a tilting means 13 such as a shaft and a bearing. The holding table 14 has an opening 15 located below the plurality of wafers 6, and also functions as a diaphragm plate. If a closing plate 16 is provided to surround the periphery in response to the tilting movement of the holding table 14, the diaphragm effect will be even better.

Note that without providing a holding stand, the cassette 7 may be hung from above the water tank so as to be tiltable so as to serve as a holding stand, or the bottom surface of the cassette 7 may also serve as an aperture plate. Water supply pipes 2a, 2
By changing the direction of the pores b so that they face the entire wafer, by improving the watertightness between the closing plate work 6 and the holding table 14, and by providing a large number of pores in the opening 15 to provide fluid resistance, the water supply pipe It is recommended that the water be uniformly distributed over the entire wafer.

To use the washing tank of the above embodiment, pure water is supplied from the water supply pipe 2a and overflowed from the weir 5 as shown in FIG. If the holding table 14 is tilted so that the device surface 6a of the wafer 6 is tilted downward, the device surface 6a will receive the dynamic pressure of pure water (washed with water). Therefore, the pure water can effectively flow onto the wafer 6, and the pure water will not flow unnecessarily into the handle 7a of the cassette 7 or into the space near the inner wall of the water tank 1 due to tilting.

When the water washing has sufficiently progressed, the valve 3 is opened as shown in FIG. 2 to drain the pure water from the drain pipe 4. At this time, when the holding table 14 is tilted in the opposite direction, the descending pure water applies dynamic pressure to the device surface 6a of the wafer 6 again.

Since drainage is to be carried out rapidly, using a drain pipe 4 with low drainage resistance, as well represented in FIG. 3, can enhance the effect of preemption during drainage.

Even if drainage is not performed as in the cascade system, if the cassette 7 is tilted and pulled up as shown in FIG. 2, dynamic pressure of pure water will be applied to the device surface 6a and the device will be thoroughly washed.

〔Effect of the invention〕

The purified water washing tank and washing method for semiconductor wafers of this invention group form a water surface by a gutter directly under the weir of the water tank to equalize the flow overflowing the weir, thereby making the streamlines and flow velocity in the water tank uniform, The openings in the holding table etc. allow pure water to flow effectively only towards the wafer, and the tilting means allows dynamic pressure of pure water to be constantly applied to the device surface in response to changes in the flow direction of the pure water relative to the wafer. By using each of the inventions alone or in combination, it is possible to improve the washing efficiency of pure water, reduce the amount of expensive pure water used, speed up the processing time, and achieve cleaner water. This has the effect that semiconductor wafers can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the pure water supply state of the embodiment, and shows the I-1 cross section in FIG. 3, FIG. 2 is a cross-sectional view showing the draining state in FIG. 1, and FIG. Partially cutaway front view of Figure 1;
FIG. 4 is a plan view of FIG. 3. DESCRIPTION OF SYMBOLS 1... Water tank, 2a, 2b... Water supply pipe, 4... Drain pipe, 5... Weir, 6... Wafer, 6a... Device surface, 7... Cassette, 11...・Gutter, 12...Water level maintenance pipe, 13...Tilt Figure 1 Figure 3 @ Figure 2 Figure 4

Claims (1)

[Scope of Claims] 1) A pure water washing tank for semiconductor wafers consisting of a water tank, a water supply pipe at the bottom of the water tank, and a weir located on the same horizontal plane at the upper edge of the water tank, wherein A pure water washing tank for semiconductor wafers, comprising a circulating gutter and a reference water level holding means for maintaining the water surface of the gutter horizontally. 2) In a pure water washing tank for semiconductor wafers consisting of a water tank, a water supply pipe at the bottom of the tank, and a weir at the upper edge of the tank, a plurality of wafers are arranged in parallel with their surfaces substantially perpendicular in the tank. A deionized water washing tank for semiconductor wafers, comprising: a diaphragm plate disposed below; and an opening provided in the diaphragm plate and located in a region below the plurality of wafers. 3) In a pure water washing tank for semiconductor wafers consisting of a water tank, a water supply pipe at the bottom of the water tank, and a weir at the upper edge of the water tank, a tank is arranged above the water supply pipe and holds the surface of the wafer almost vertically. 1. A pure water washing tank for semiconductor wafers, comprising: a holding table for tilting the holding table; and a tilting means for tilting the holding table. 4) The pure water washing tank for semiconductor wafers according to claim 2 or 3, characterized in that a drain pipe is provided at a lower part of the water tank. 5) The wafer is immersed in a water washing layer consisting of a water tank, a water supply pipe at the lower part of the water tank, and a weir at the upper edge of the water tank with the surface of the wafer almost vertically, and pure water is supplied from the water supply pipe and the weir is connected to the weir. In the semiconductor wafer washing method of washing the wafer with water overflowing from the wafer, when the pure water flows upward with respect to the wafer, the device surface of the wafer is tilted downward;
A method for washing a semiconductor wafer with water, characterized in that when the wafer is taken out from the water tank, the device surface is tilted upward when the pure water flows downward with respect to the wafer.